The direct link to the pictures used for the dvd.box.sk test shows, that not one single picture of Intervideo Copy DVD, according to you the ones with ending dvdc matches the file size of the original file.
Actually the file, that matches exactly the original file size is sklad_inst.jpg, which belongs most likely to InstantCopy, same for the hala_orig.jpg and hala_inst.jpg.
For the ohen series of pics, the Instant file matches the Intervideo one and the original file size is shared by ohen_dvdx.jpg and ohen_vr.jpg.
Do we talk about the same files here? I would sugest you take a closer look to the filesize again.